A Dorset police spokesman said: "The body of a male has been recovered from the sea by the coastguard – at approximately 5.30pm today. This is believed to be one of the missing fishermen from the vessel Purbeck Isle."

An air-and sea-search was launched involving three navy ships and a coastguard helicopter, but they could find no trace of the boat or any wreckage until they found the body, which has not yet been identified.

The three men have been named locally as skipper David McFarland, 37, and crewmen Jack Craig, 22 and Robert Prowse, 23. Prowse's mother, Maxine, said: "I'm just listening to the news now and waiting. He's a hard-working lad. He has a lot of friends."

Coastguards are examining a sonar image of an object of a similar size to Purbeck Isle on the seabed 55 metres (180ft) down, taken by a survey ship. A spokesman, Fred Caygill, said: "What we have is an image from 55 metres down, but it can't be clearly identified. We had a survey ship in the area with a sonar and it scanned the seabed. It did give us an image from about 10 miles south of Portland Bill, but it is impossible to decipher."

According to local people the crew had been potting for whelks. Ron Brown, a skipper, highlighted the dangers, saying: "If you are pulling in pots and one gets stuck, it can pull the boat down and then if a wave hits you and everyone is on deck, there might not be time to raise the alarm."

Dave Pitman, another skipper, said: "They were working with whelking pots as I understand it. They were moving the gear from one place to another, which is a normal operation. We just all hope they are safe."

Andy Alcock, the secretary of the Weymouth and Portland Fishermen and Licensed Boatmen Association, said: "There was a liferaft on board and there is a chance the men are in that and have been blown up and down the Channel and are awaiting rescue."

The alarm was raised late on Thursday afternoon when the 11-metre (36ft) boat failed to return to port in Weymouth. There had been no word from the fisherman for nine hours since they left the harbour at 8.30am. Coastguards tried to contact the crew by radio but were met with silence. Two British naval vessels including the type 42 destroyer HMS York and a US navy supply vessel joined the search .